This invention relates to apparatus for feeding paperboard blanks (such as corrugated blanks or sheets) one by one from the bottom of a stack of blanks to nip rolls (usually referred to in the art as feed rolls) for feeding to box-making machinery, such as printing, cutting, slotting, folding, or gluing machinery or the like. Such apparatus is known in the art as a feed table.
Most commercially available feeders include what is referred to in the art as kicker feed -- a pusher member which is reciprocated to engage the trailing end of the blank to be fed, push such blank to the nip rolls, decelerate and come to the end of its stroke and then to return to its initial position to engage the trailing end of the next blank. Kicker feed machines will often jam or misfeed if, among other reasons, a blank is warped or the edge of a blank is crushed or ragged. Such jams necessitate unloading the hopper which causes significant production delays. Moreover, the moving pusher bar, in close proximity to the operator's hands, can be a safety hazard.
One commercially available feeder which does not rely on kicker feed includes a reciprocated suction shuttle member. This machine is described in Bishop et al U.S. Pat. No. 3,105,681. This feeder requires nip rolls which are partially relieved to accommodate the forward position of the shuttle member. Such partially relieved rolls present a deflection problem especially on wide machines. These machines also involve use of a relatively high vacuum (e.g. 10 psi of vaccum), involving a relatively expensive vacuum pump instead of a simple blower. The reciprocation involved in the operation of the Bishop feeder has a tendency to move the blank to be fed away from the gates thereby causing it to be fed out of register. The term "register" is used herein to mean that the leading edge of the blank being fed always enters the nip of the feed rolls at exactly the same point in each machine cycle.
It is an object of this invention to provide novel apparatus which does not have the operating and safety problems of kicker feed and which does not require relieved nip rolls or extremely high degrees of vacuum and which does not have a reciprocated shuttle member and therefore has an advantage in the consistency with which it feeds blanks in register.